Conventional mechanical and electromechanical power switches suffer from disadvantages relating to high levels of noise and spike voltages that are generated when electrical loads are turned on/off. These problems can be overcome through the use of a solid state power controller (SSPC), i.e., an electrical power distribution apparatus utilizing one or more solid state switching devices. Furthermore, SSPCs have the advantages of occupying less space, being light-weight and being more reliable.
Generally, an SSPC may operate in one of two modes with respect to an electrical load: a power controller mode, and a circuit breaker mode. In the power controller mode, an SSPC is configured to turn power on and off for its electrical load based on control commands received, e.g., from a microcontroller. Alternatively, in the circuit breaker mode, an SSPC continuously applies power to the electrical load until corresponding load current becomes excessive, e.g., because of a short circuit, or an overload condition. When the SSPC is operating in the circuit breaker mode, it may be configured (e.g., by the microcontroller) to operate according to a particular load current level, such that the SSPC switches power off when the current in the electrical load exceeds the particular load current level.
SSPC technology can be used in various types of power distribution systems. For example, an aircraft may incorporate an SSPC-based Secondary Electrical Power Distribution System (SEPDS), which uses programmable SSPC devices in place of traditional electromechanical circuit breaker technology. This type of SEPDS provides benefits to the aircraft in terms of load management, fault isolation, diagnostic health monitoring, and improved flexibility to accommodate modifications and system upgrades.
However, an aircraft SEPDS is one example of a high-reliability system whose design requires redundancy to ensure that safety and reliability targets are met when the system is integrated. As such, there should be some redundancy or backup functionality provided for the control of SSPCs in such systems.